Pension Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 25, 2017	Mar. 26, 2016	Mar. 25, 2017	Mar. 26, 2016
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1,041	$ 1,260	$ 2,082	$ 2,521
Expected return on plan assets	(537)	(854)	(1,075)	(1,709)
Amortization of net loss (gain)	1,300	1,475	2,600	2,609
Net periodic benefit cost	1,804	1,881	3,607	3,421
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	96	130	193	260
Amortization of prior service credits	0	(100)	0	(200)
Amortization of net loss (gain)	(97)	(74)	(194)	(149)
Net periodic benefit cost	$ (1)	$ (44)	$ (1)	$ (89)